This invention relates to monolithic integrated optical components made of Column IV alloys, particularly active, waveguided, electrooptical components that emit, amplify, modulate, or detect infrared light with high efficiency.
Monolithic integration on silicon requires that all components are constructed from elements or alloys in Column IV of the periodic table. For silicon-based monolithic opto-electronic components, such as the components interconnected on the opto-electronic superchip, efficient light emitters, especially laser diodes, and efficient modulators do not exist today, mainly because of the indirect bandgap of Si, of Ge, and of bulk Column IV alloys. In other words, "complete optical functionality" on a monolithic chip is prevented today by the lack of key photonic components. The indirect gap of prior-art materials means that the absorption edge of the material is broad. Also, indirectness prevents efficient recombination of electrons and holes across the gap (needed for strong luminesence).
There is a need to modify the band structure of Column IV materials so that optical transitions across the forbidden gap become strongly allowed, and so that the optical absorption spectrum becomes "sharp".
A temporary solution has been to go outside of Column IV for materials (to the III-V semiconductors, for example), and to join those materials to silicon. This "hybrid" approach to Si opto-electronics is the integration of various "non-IV" photonic components with silicon electronics by means of soldering, bonding, gluing, etc. However, the hybrid solution may not be satisfactory in the long run because the cost of hybrid chips may prove to be higher than that of monolithic chips. Monolithic integration of Column IV photonic alloys with Column IV electronics is expected to be very cost effective and reliable.